BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 351 



Witte's peptone, 0.5 per cent sodium chloride, 0.5 per cent Liebig's 

 meat extract, 0.5 per cent potassium nitrate (Merck). Good growth 

 took place in these tubes after five days at 25 to 27 C. They were 

 tested by the KI H 2 S0 4 starch method as recommended by E. F. Smith.* 

 Not the slightest nitrate formation was shown in any of the tests. 



Enzymes. The walnut organism produces at least four enzymes, 

 diastatic (starch-destroying), cytohydrolytic (cellulose-dissolving), ren- 

 net (casein-forming), proteolytic (peptonizing). Professor Pierce 

 statesf in his article on this disease that he found that these enzymes 

 are especially active at a temperature between 65 to 75 F., and this 

 agrees very well with our study of growth of the organism on potato 

 slices and the accompanying fermentation zone. 



Attention was called by Professor Pierce to the marked similarity 

 between the organisms of walnut bacteriosis and the black rot of the 

 cabbage. While few comparative studies have been made, yet the 

 cultural characteristics of the two are very similar indeed. The few 

 cross-inoculations made with Pseudomonas campestris on walnut and 

 Pseudomonas juglandis on cabbage show that the pathogenic proper- 

 ties are distinct. The walnut organism also grows more readily on 

 plant juices. 



The group number of the organism, in accordance with the system 

 prepared by the American Society of Bacteriologists, is 211.3332513. 

 It will be observed that this is identical with that of Pseudomonas 

 campestris. 



ARTIFICIAL INOCULATIONS. 



Methods. Inoculations have been successfully made at various seasons 

 of the year and in two different ways, by puncture and by atomizing. 

 The puncture method is the most likely to give positive results. A steri- 

 lized needle is used to transfer some of the germs from a pure culture 

 into a wound made by a slight pricking of the surface. The atomizing 

 method was used also quite effectively on the young nuts, but gave no 

 results on foliage or the young shoots. A young pure culture of the 

 walnut blight organism grown on potato for about three days was mixed 

 with distilled water and the mixture sprayed on the nuts or shoots with 

 an ordinary medical atomizer, without injuring the tissue. This experi- 

 mental work has extended over two seasons. The season of 1907 was 

 one favorable for blight development from natural infections, while that 

 of 1908 produced very little walnut blight. The time and results from 

 atomizing during 1907 and 1908 are given in tables which follow. 



Atomizing on Late Tree. The results summarized in the following 



* Bacteria in Relation to Plant Diseases. 



t Bailey's Encyclopedia of American Horticulture, p. 1961. 



